This is an application for a NEUROSCIENCE WORK GROUP IN MENTAL HEALTH that will bring together eleven senior investigators for collaborative research on the neurohormonal mechanisms of salt appetite in the rat. Recent behavioral-endocrinological research has demonstrated that salt appetite is an hormonally induced behavior. It is aroused by the synergistic action in the brain of angiotensin and aldosterone which are also the hormones of renal sodium conservation. The Work Group will combine behavioral- endocrinological methods with state-of-the-art biological techniques (cytosol receptor analysis, membrane pharmacology, microiontophoresis and electrophysiology, and cellular biochemistry) in a broad-ranging reductionist analysis of the neural mechanisms by which angiotensin and aldosterone act to arouse a specific motivated behavior that depends for its expression on a single sensory channel (the salt taste). Six Projects are proposed. They are closely integrated around the central question: What is the cellular and molecular nature of the neural mechanism by which angiotensin and associated hormones (aldosterone and atrial natriuretic hormone) mobilize salt. appetite?